styrene

styrene - T heoret. ehim. Aeta (Ber].) 3, t6.t-t73 (t965) T...

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Theoret. ehim. Aeta (Ber].) 3, t6.t---t73 (t965) The Institute for Solid State Physics, The University of Tokyo Vacuum Ultraviolet Spectra of Styrene, Bcnzaldehyde, Acetophenonc, and Benzonitrile By KATSUMI KIMURA ~ and SABURO ~AGAKURA The vacuum ultraviolet absorption spectra of styrene, benzaldehyde, aeetophenone and benzonitrile have been measured in the wavelength region of 1500 to 2200 ]~. The absorption bands in the vacuum ultraviolet region appear at 200, 196, t89, t80 and 163 m/z for styrene; at 195, 186, '178 and 165 m# for benz~ldehyde; at 196, 191,179 and t67 m/z for aeetophenone; at 187.5, 180 and 167 m# for benzonitrile. Theoretical studies of n-electron structures have been carried out with styrene, benzal- dehyde and acetophenone by considering eonfigurational interactions among the ground, locally excited, and charge-transfer configurations. The calculated transition energies and oscillator strengths are in good agreement with the observed values. The theoretical results show that the contribution of the charge-transfer configuration amounts to 58 and 68% in the excited states of the 238 m# band of styrene and of the 232 m/z band of benzaldehyde respec- tively. This means that these two bands may be regarded as the intramolecular charge- transfer band. The electron affinity of the C = C and C = O groups were determined to be respectively -0.84 and -t.20 eV from the present analysis of the ultraviolet spectra. Die Vakuum-Ultraviolettspektren yon Styro], Benzaldehyd, Acetophenon and Benzoni- tril im Bereich yon 1500 bis 2200 A wurden gemessen: 200, 196, 189, t80 und t63 m# fiir Styrol, 195, 186, 178 und 165 in#. fiir Benzaldehyd, 196, 191,179 und 167 m# fiir Acetophenon und 187,5, 180 und 167 ml~ ffir Benzonitril im Vakuum-UV-Bereich. Berechnungen der z-Elektronensysteme der drei erstgenannten Verbindungen warden unter Einsehlul~ von Konfigurationen mit und ohne Charge Transfer durchgeffihrt und ergaben ~bergangsenergien und Oszillatorst~rken, die mit den MeBwerten bcfriedigend fibereinstim- men. Zum oberen Zustand der 238 mt~-Bande yon Styrol trEgt die Charge Transfer Konfigura- tion 580/0 bei, und zu dem der 232 m/z-Bande yon Benzaldehyd sogar 68%, woraus hervorgeht, dab es sich bei diesen beiden Banden um intramolekulare Charge Transfer Banden handelt. Die Elektronenaffinit~t der C = C- und der C = O-Gruppe betr~gt nach diesen Berech- nungen -0,84, bzw. -1,20 eV. Nons avons mesur5 les spectres d'absorption du styrene, du benzald~hyde, de l'ac~to- ph~none et du benzonitrfle entre 1500 et 2200 A. Les bandes se situent s 200, 196, 189, 180 et t63 m,u pour le styrene; s 195, t86, 178 et 165 m# pour le benzald6hyde; s 196, 191, 179 et t67 m/~ pour [email protected] et ~ 187,5, 180 et 167 m~ pour le bentonitrile. Les structures ~-61ectroniques des trois premieres [email protected] out @t6 ~tudi~es, en consid@- rant l'interaction entre les configurations forndamentales, loculement [email protected] et exeit6es avec transfert de charge. Les @nergies et forces oscillatrices calcul~es s'accordent bien aux valeurs observ6es. Le calcul montre que la configuration s transfert de charge entre avec 58% duns la bande & 238 mp du styrene, et avec 68o/0 duns ceUe ~ 232 m# du [email protected] Par consequent ces deux bandes peuvent ~tre attributes au transfert de charge [email protected]
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This note was uploaded on 04/09/2011 for the course CHEM 99 taught by Professor Staff during the Fall '08 term at UCSB.

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styrene - T heoret. ehim. Aeta (Ber].) 3, t6.t-t73 (t965) T...

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